Hi nenad,
not problem with finding the captcha refresh button.
There is one know bug in Visforms for 3.0.0 (therefore still a beta).
It's easy to fix.
See the instructions here
www.vi-solutions.de/de/kunena/19-joomla-...-too-many-fields#587
The background is, that I switched from Mootools Javascript framework (which was default with Joomla! 2.5 ) to jQuery framework (which is default in Joomla! 3) and I just missed one step. Most templates still load the mootools and therefore the bug was not so easy to discover. But pure bootstrap templates (as yours) become more popular and they do not load mootools anymore. So these templates "see" the bug.
I will fix this, of course, with the next Version of Visforms, but making a new Version is a lot of work (especially the testing). Therefore I want to wait a bit longer with that.
Kind Regards,
Aicha